Some unfortunate users have suffered from email troubles with Mail since OS X Mavericks' launch, something addressed with 10.9.1 after a sharp focus on the issue by Apple. Still, some users' woes have continued, and retrieving emails is harder than it needs to be. Apple published a manual workaround for these users today, though it hasn't said when the (next) fix will be available.
If users were hoping for an easier method to get around the problem than currently in circulation, that hope is unfounded, unfortunately. Apple published a workaround method today that involves taking Mail offline and, in an effort to streamline it, offers instruction on adding a shortcut to perform the task.
To deal with the problem, users are advised to select Mailbox -> Take All Accounts Offline, followed by "Get All New Mail" under the same menu. This should cause it to pull in new messages that otherwise won't be received until an action is taken -- commonly quitting and reopening Mail.
For those who want to make a shortcut to streamline the process, Apple says to open Customize Toolbar under the View menu, then drag the "Take All Accounts Offline" over to the toolbar and click "Done". After doing this, the workaround becomes as simple as clicking the new shortcut button, then clicking "Check Mail".
SOURCE: Mac Rumors